If you mean that 'click' noise which intrudes onto the sound, you could be running your pickups too high. Most basses come from the factory set-up for fingerstyle or pick players, so the pickups are a little too close to the strings for slap, so you end up with a really clicky tone. just drop the pickups a little, just a few mm. test it as you go to get just the right response.

My basses have all had to be tweaked to accomodate my playing style, including my Stingray, which even clicked when I played fingerstyle (I'm fairly heavy handed)